The present invention relates to a Bourdon-tube pressure gauge wherein the indicator has a rack portion which is swung within a range such that the rack portion is always engaged with a needle gear.
A conventional Bourdon-tube gauge is disclosed in U.S. Pat. Nos. 6,314,816 and 5,567,883 respectively and includes an indicator which is pivotally connected to a frame and a needle gear is connected. The indicator includes a rack portion which is expected to be engaged with the needle gear when the Bourdon tube is deformed to rotate the indicator. However, it is noted that the rack portion is not engaged with the needle gear when the indicator is positioned at least one of the two extreme positions. In other words, when an extraordinary high or low pressure is tested and the Bourdon tube is deformed dramatically, the two extreme positions of the indicator will let the rack portion disengage from the needle gear. These two extreme positions imply that the pressure tested is beyond the desired precision of the Bourdon-tube gauge.
The present invention intends to provide a Bourdon-tube pressure gauge wherein the range of the swing of the indicator is limited to ensure the rack portion of the indicator is always engaged with the needle gear whenever the pressure tested is high or low.
In accordance with one aspect of the present invention, there is provided a structure for Bourdon-tube pressure gauge which comprises a casing with a test tip extending from the casing and a frame is fixedly positioned in the casing. A needle gear and a limit bar are respectively connected to the frame. A Bourdon tube has one end thereof connected to the test tip and the other end of the Bourdon tube is connected to a link. An indicator is pivotally connected to the frame and a first end of the indicator is pivotally connected to the link and a second end of the indicator has a rack portion which is engaged with the needle gear. A concave portion is defined in a side of the indicator and a protrusion portion extends from the side of the indicator. The rack portion is engaged with the needle gear when the concave portion is engaged with the limit bar.
The primary object of the present invention is to provide a Bourdon-tube pressure gauge wherein the rack portion of the indicator is engaged with the needle gear all the time no matter how high or low of the pressure is tested.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.